Ornithine decarboxylase (ODC) plays a major role in the growth and differentiation of cells. An adrenal cell line, Y-1, with mutants available in ACTH receptor-adenylate cyclase coupling and cAMP-dependent protein kinase, will be used to study the hormonal regulation of ODC in the adrenal cell. The steroidogenic, hypertrophic stimulants, ACTH and cAMP, as well as the mitogenic factor from the N-terminus proopiocortin will be employed to study the regulation of ODC during both processes. The goal of this project is to elucidate the intracellular mechanisms governing ODC expression after hormonal stimulation of the adrenal. The characteristics of enzyme induction will first be established on a cellular level. Then biochemical and immunochemical techniques will be employed to establish the changes in intracellular events which have supported the increase in enzyme activity. The amount of ODC enzyme protein will be quantitated and the synthetic and turnover rates of the enzyme protein determined. Changes in the cellular content of ODC mRNA will be assessed by in vitro translation analysis and by hybridization studies. The synthesis rated and species number and type of the ODC mRNA will be determined. This project should furnish new information regarding the regulation of the adrenal by trophic and mitogenic hormones.